An ink jet print head has a nozzle face comprising at least one array of nozzle openings for jetting out droplets of ink in a printing process.
When an ink jet print head is not in use for a period of time, the nozzle face needs to be protected to keep the nozzle openings in an optimal condition for again jetting out droplets of ink when printing is resumed.
In case the nozzle face is left unprotected while an ink jet print head is inactive, ink inside an ink channel ending at a nozzle opening may disadvantageously interact with an environment of the print head. Ink may for instance dry out, or polymerize due to stray light from the environment, which may leave depositions inside the nozzle opening. Depending on the type of ink used, also, moisture from the environment may condense onto the nozzle face and interact with ingredients of the ink inside an ink channel to form depositions around a nozzle opening. Depositions inside and around a nozzle opening may adversely affect operation of the nozzle opening when printing is resumed, for instance by blocking the ejection of an ink droplet, or by causing an ejected ink droplet to be misdirected.
A known method of protecting a nozzle face comprises pressing a sealing member such as a capping sheet or a gasket against the nozzle face, so that the nozzle openings are sealed off from the environment. Such method is also known as capping. With this method, ink may remain on the sealing member after removal from the nozzle face. The remaining ink may age, and may for instance become sticky, and gather dust. Aged ink and dust may soil the nozzle face and clog up nozzle openings during further use of the sealing member for capping the nozzle face. As a consequence, a sealing member as described needs to be frequently cleaned.
Another known method comprises sealing off the nozzle face using a wet pad soaked with a soaking solution. With this method, fibers from the wet pad may get transferred to the nozzle face and then clog up nozzle openings. A wet pad needs to be replaced at times, and the soaking solution needs to be periodically refreshed.
Yet another known method comprises immersing the nozzle face in a liquid bath. With this method, liquid remaining on the nozzle face after removal of the print head from the liquid bath may contaminate a recording medium when printing is resumed, and may also affect the formation of ink droplets at a nozzle opening. Frequent cleaning of a nozzle face is therefore required to remove aged liquid from the nozzle face.
The present invention aims to provide an improved method of protecting a nozzle face of an ink jet print head during a period of inactivity. The present invention particularly aims to provide a protection method which is effective without adverse effects on the operation of a nozzle opening when printing is resumed. A further objective is to provide a method of protecting a nozzle face which can be relatively simply implemented.